Method For Manufacturing Cable-Type Secondary Battery

ABSTRACT

The present invention relates to a method for manufacturing a cable-type secondary battery comprising an electrode that extends longitudinally in a parallel arrangement and that includes a current collector having a horizontal cross section of a predetermined shape and an active material layer formed on the current collector, and the electrode is formed by putting an electrode slurry including an active material, a polymer binder, and a solvent into an extruder, by extrusion-coating the electrode slurry on the current collector while continuously providing the current collector to the extruder, and by drying the current collector coated with the electrode slurry to form an active material layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/KR2011/000288 filed on Jan. 14, 2011, published in Korean, whichclaims priority from Korean Patent Application No. 10-2010-0009438 filedon Feb. 2, 2010, and Korean Patent Application No. 10-2011-0003202 filedon Jan. 12, 2011, the entire contents of which are incorporated hereinby reference.

TECHNICAL FIELD

The present invention relates to a method for manufacturing a cable-typesecondary battery of free shape adaptation, and more particularly, to amethod for manufacturing a cable-type secondary battery using anextruder.

BACKGROUND ART

Secondary batteries are devices capable of storing energy in chemicalform and of converting into electrical energy to generate electricitywhen needed. The secondary batteries are also referred to asrechargeable batteries because they can be recharged repeatedly. Commonsecondary batteries include lead accumulators, NiCd batteries, NiMHaccumulators, Li-ion batteries, Li-ion polymer batteries, and the like.When compared with disposable primary batteries, not only are thesecondary batteries more economically efficient, they are also moreenvironmentally friendly.

The secondary batteries are currently used in applications requiring lowelectric power, for example, equipment to help the start-up of vehicles,portable devices, tools, uninterruptible power supplies, and the like.Recently, as the development of wireless communication technologies hasbeen leading to the popularization of portable devices and even to themobilization of many kinds of conventional devices, the demand for thesecondary batteries is dramatically increasing. The secondary batteriesare also used in environmentally friendly next-generation vehicles suchas hybrid vehicles and electric vehicles to reduce the costs and weightand to increase the service life of the vehicles.

Generally, the secondary batteries have a cylindrical, prismatic, orpouch shape. This is associated with a manufacturing process of thesecondary batteries in which an electrode assembly composed of an anode,a cathode, and a separator is mounted in a cylindrical or prismaticmetal case or a pouch-shaped case of an aluminum laminate sheet, and inwhich the case is filled with electrolyte. Because a predeterminedmounting space for the electrode assembly is necessary in this process,the cylindrical, prismatic or pouch shape of the secondary batteries isa limitation in developing various shapes of portable devices.

To fulfill this need, suggestions have been made to develop linearbatteries having a very large ratio of length to cross-sectionaldiameter. Korean Patent Registration No. 0804411 discloses a method formanufacturing a linear battery including a plurality of anodes and aplurality of cathodes with separators interposed therebetween. KoreanPatent Registration No. 0742739 discloses a thread-type flexible batteryincluding cathode threads and anode threads in which hot dipping,sputtering, chemical vapor deposition, and the like is used as a coatingtechnique for electrodes and electrolyte. However, conventionalnon-continuous coating techniques are not suitable for cable-typesecondary batteries having a linear structure extending longitudinally.There is a need for continuous coating suitable for cable-type secondarybatteries.

SUMMARY OF THE INVENTION

It is an aspect of the present invention to provide continuous coatingsuitable for cable-type secondary batteries having a linear structureextending longitudinally.

In an embodiment of the present invention, provide is a method formanufacturing a cable-type secondary battery having an electrode thatextends longitudinally in a parallel arrangement and that includes acurrent collector having a horizontal cross section of a predeterminedshape and an active material layer formed on the current collector, themethod comprising forming the electrode, in which the forming of theelectrode includes putting an electrode slurry including an activematerial, a polymer binder, and a solvent into an extruder;extrusion-coating the electrode slurry on the current collector whilecontinuously providing the current collector to the extruder; and dryingthe current collector coated with the electrode slurry to form an activematerial layer.

Preferably, the current collector may be made from stainless steel,aluminum, nickel, titanium, sintered carbon, and copper; stainless steelsurface-treated with carbon, nickel, titanium, and silver;aluminum-cadmium alloys; non-conductive polymer surface-treated with aconductive material; or conductive polymers. The conductive material maybe any one selected from the group consisting of polyacetylene,polyaniline, polypyrrole, polythiophene, polysulfur nitride, indium thinoxide (ITO), silver, palladium, nickel, and copper, or mixtures thereof.The conductive polymer may be any one selected from the group consistingof polyacetylene, polyaniline, polypyrrole, polythiophene, andpolysulfur nitride, or mixtures thereof.

The active material may be an anode active material that may be any oneselected from the group consisting of carbonaceous materials;lithium-containing titanium composite oxides (LTOs); metals (Me)including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, and Fe; alloys of the metals(Me); oxides (MeOx) of the metals (Me); and composites of the metals(Me) and carbon, or mixtures thereof, or may be a cathode activematerial that may be any one selected from the group consisting ofLiCoO₂, LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMnCoO₂, andLiNi_(1-x-y-z)CO_(x)M1 _(y)M2 _(z)O₂ (each of M1 and M2 is independentlyany one selected from the group consisting of Al, Ni, Co, Fe, Mn, V, Cr,Ti, W, Ta, Mg, and Mo, and each of x, y, and z is independently anatomic fraction of each component in the oxide, where 0≦x<0.5, 0≦y<0.5,0≦z<0.5, x+y+z≧1), or mixtures.

The polymer binder may be any one binder polymer selected from the groupconsisting of polyvinylidene fluoride (PVdF)-co-hexafluoropropylene,polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate(PMMA), polybutylacrylate, polyacrylonitrile (PAN),polyvinylpyrrolidone, polyvinylacetate (PVAc), polyethylene-co-vinylacetate, polyethylene oxide (PEO), polyarylate, cellulose acetate,cellulose acetate butyrate, cellulose acetate propionate,cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose,cyanoethylsucrose, pullulan, and carboxyl methyl cellulose, or mixturesthereof.

The method for manufacturing a cable-type secondary battery of thepresent invention may further include putting a solid electrolytematerial into the extruder, and extrusion-coating the solid electrolytematerial on the electrode while continuously providing the electrode tothe extruder, to form an electrolyte layer around the electrode.

The solid electrolyte material may include an electrolyte selected fromthe group consisting of a gel polymer electrolyte of PEO, PVdF, PMMA,PAN, or PVAc, and a solid polymer electrolyte of PEO, polyphenyleneoxide (PPO), polyetherimide (PEI), polyethersulfone (PES), or PVAc.

The solid electrolyte material may further include a lithium salt, andthe lithium salt may be any one selected from the group consisting ofLiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPF₆, LiCF₃SO₃, LiCF₃CO₂,LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, chlorineborane lithium, aliphatic lower lithium carbonate, and 4-phenyl lithiumborate, or mixtures thereof.

According to another aspect of the present invention, a method formanufacturing a cable-type secondary battery may include forming ananode by extrusion-coating an electrode slurry on a current collector,the anode having a horizontal cross section of a predetermined shape andextending longitudinally; forming an electrolyte layer around theperimeter of an inner electrode by extrusion-coating a solid electrolytematerial, the inner electrode including at least two anodes arranged inparallel; forming an outer electrode around the electrolyte layer, theouter electrode being a tubular cathode having a horizontal crosssection of a predetermined shape; and forming a protection coatingaround the outer electrode.

According to still another aspect of the present invention, a method formanufacturing a cable-type secondary battery may include forming ananode having an electrolyte layer thereon by sequentiallyextrusion-coating an electrode slurry and a solid electrolyte materialon a current collector, the anode having a horizontal cross section of apredetermined shape and extending longitudinally; forming an outerelectrode having a cathode active material layer, the cathode activematerial layer surrounding the perimeter of the inner electrodeincluding at least two anodes arranged in parallel; and forming aprotection coating around the outer electrode.

According to still yet another aspect of the present invention, a methodfor manufacturing a cable-type secondary battery may include forming ananode having a first electrolyte layer thereon by sequentiallyextrusion-coating an electrode slurry and a solid electrolyte materialon a current collector, the anode having a horizontal cross section of apredetermined shape and extending longitudinally; forming a cathode byextrusion-coating an electrode slurry on a current collector; forming asecond electrolyte layer around the perimeter of an inner electrode byextrusion-coating a solid electrolyte material, the inner electrodeincluding the anode and the cathode arranged in parallel; and forming aprotection coating around the second electrolyte layer.

According to a method for manufacturing a cable-type secondary batteryof the present invention, extrusion coating using an extruder effectscontinuous coating, and thus is suitable for manufacturing cable-typesecondary batteries extending longitudinally. Also, the thickness of acoating layer is easily controlled by adjusting a linear velocity of acurrent collector or an extrusion rate of an extruder.

DESCRIPTION OF DRAWINGS

Other objects and aspects of the present invention will become apparentfrom the following description of embodiments with reference to theaccompanying drawing in which:

FIG. 1 is a schematic view of an extruder;

FIG. 2 is a view illustrating wire-type extrusion coating using anO-die;

FIG. 3 is a cross-sectional view illustrating a cable-type secondarybattery having an electrolyte layer interposed between an innerelectrode and an outer electrode according to an embodiment of thepresent invention;

FIG. 4 is a cross-sectional view illustrating a cable-type secondarybattery having an electrolyte layer interposed between an innerelectrode and an outer electrode according to another embodiment of thepresent invention;

FIG. 5 is a cross-sectional view illustrating a cable-type secondarybattery having an electrolyte layer around an inner electrode accordingto still another embodiment of the present invention; and

FIG. 6 is a cross-sectional view illustrating a cable-type secondarybattery having a first electrolyte layer and a second electrolyte layeraccording to still yet another embodiment of the present invention.

DETAILED DESCRIPTION

Hereinafter, the present invention will be described in detail withreference to the accompanying drawings. The description proposed hereinis just a preferable example for the purpose of illustrations only, notintended to limit the scope of the invention, so it should be understoodthat other equivalents and modifications could be made thereto withoutdeparting from the spirit and scope of the invention.

A cable-type secondary battery of the present invention has a horizontalcross section of a predetermined shape and a linear structure extendinglongitudinally. The cable-type secondary battery comprises an electrodeextending longitudinally in a parallel arrangement and the electrodeincludes a current collector having a horizontal cross section of apredetermined shape and an active material coated on the currentcollector. Here, the predetermined shape is not limited to a specificshape, and may include any shape without departing from the spirit andscope of the present invention. Specifically, the horizontal crosssection may have a circular or polygonal shape, wherein the circularshape may be a circular shape of geometrical symmetry or an oval shapeof geometrical asymmetry, and the polygonal shape may be a triangular,square, pentagonal, or hexagonal shape. The cable-type secondary batteryhas flexibility and free shape adaptation, and thus may be applied tovarious shapes of portable devices. A method for manufacturing thecable-type secondary battery comprises forming an electrode byextrusion-coating an electrode slurry on a current collector, theelectrode slurry including an active material, a polymer binder, and asolvent.

The extrusion coating is performed by coating and extruding a coatingsolution on the surface of a substrate through an extruder in acontinuous way, and is less subject to limitation on the length of thesubstrate and enables continuous coating. Referring to FIG. 1, generallyan extruder has a hopper 1, a cylinder 2, and a die 5. Typically,according to extrusion coating, a coating raw material is put into thehopper 1 and is transmitted toward the die 5 by the rotation of a screw3 in the cylinder 2 while the coating raw material is molten into acoating solution as it goes through the cylinder 2 where a constanttemperature is maintained, and the coating solution is coated on thesubstrate through the die 5 mounted at a front part of the cylinder 3.The cable-type secondary battery has shape characteristics of a linearstructure extending longitudinally and a predetermined horizontal crosssection, and thus is suitable for the application of continuous coating,in particular, extrusion coating.

The electrode extending longitudinally is formed by putting an electrodeslurry into the hopper 1 of the extruder, by mixing and transmitting theelectrode slurry to the die 5 by the rotation of the screw 3 in thecylinder 2, and by extrusion-coating the electrode slurry on a currentcollector through the die 5 mounted at a front part of the cylinder 2while the current collector is provided to the extruder. The currentcollector for forming an electrode may be a wire-type current collector.The present invention is not limited to a specific type of die based onthe type of the current collector. However, in the case of a wire-typecurrent collector, an electrode slurry may be coated on the surface of acurrent collector while the current collector goes through a tubularO-die (See FIG. 2). The electrode slurry put into the extruder isprovided through a coating material providing unit 11, is dischargedthrough an O-die 10, and is extrusion-coated on a wire-type currentcollector 12 inserted into the O-die 10. In this instance, the thicknessof a coating layer may be easily controlled by adjusting the density oran extrusion rate of the electrode slurry, or a linear velocity of thecurrent collector that represents a supply rate of the current collectorto the extruder.

Preferably, the current collector may be made from stainless steel,aluminum, nickel, titanium, sintered carbon, and copper; stainless steelsurface-treated with carbon, nickel, titanium, and silver;aluminum-cadmium alloys; non-conductive polymers surface-treated with aconductive material; or conductive polymers. The conductive material mayinclude polyacetylene, polyaniline, polypyrrole, polythiophene,polysulfur nitride, indium thin oxide (ITO), silver, palladium, nickel,and copper. The conductive polymer may include polyacetylene,polyaniline, polypyrrole, polythiophene, and polysulfur nitride.

The electrode slurry may include an active material, a polymer binder,and an organic solvent uniformly mixed therein, and may further includea conductive material. In this instance, the electrode slurry having itscomponents uniformly mixed therein may be put into the extruder.Alternatively, the active material, the polymer binder, and the like mayeach be put into the extruder and then mixed with each other in theextruder. Preferably, drying may follow extrusion coating to remove thesolvent.

The active material includes an anode active material and a cathodeactive material. The anode active material may include, but is notlimited to, carbonaceous materials; lithium-containing titaniumcomposite oxides (LTOs); metals (Me) such as Si, Sn, Li, Zn, Mg, Cd, Ce,Ni, and Fe; alloys of the metals (Me); oxides (MeOx) of the metals (Me);and composites of the metals (Me) and carbon. The cathode activematerial may include, but is not limited to, LiCoO₂, LiNiO₂, LiMn₂O₄,LiCoPO₄, LiFePO₄, LiNiMnCoO₂, and LiNi_(1-x-y-z)Co_(x)M1 _(y)M2 _(z)O₂(each of M1 and M2 is independently any one selected from the groupconsisting of Al, Ni, Co, Fe, Mn, V, Cr, Ti, W, Ta, Mg, and Mo, and eachof x, y, and z is independently an atomic fraction of each component inthe oxide, where 0≦x<0.5, 0≦y<0.5, 0≦z<0.5, x+y+z≦1).

The polymer binder aids to bind the active material to the currentcollector, and may include polyvinylidene fluoride(PVdF)-co-hexafluoropropylene, polyvinylidenefluoride-co-trichloroethylene, polymethylmethacrylate (PMMA),polybutylacrylate, polyacrylonitrile (PAN), polyvinylpyrrolidone,polyvinylacetate (PVAc), polyethylene-co-vinyl acetate, polyethyleneoxide (PEO), polyarylate, cellulose acetate, cellulose acetate butyrate,cellulose acetate propionate, cyanoethylpullulan,cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose,pullulan, and carboxyl methyl cellulose.

The conductive material that may be further included in the electrodeslurry is used to further improve conductivity of the active material,and the present invention is not limited to a specific type ofconductive material if the conductive material has conductive propertiesand does not bring about a chemical change in the battery. For example,the conductive material may include graphite, carbon black, conductivefibers such as carbon fibers or metal fibers, fluorocarbons, metalpowder such as aluminum powder or nickel powder, conductive whisker suchas zinc oxide, potassium titanate, conductive metal oxides such astitanium oxide, and conductive materials such as polyphenylenederivatives. The present invention is not limited to a specific type oforganic solvent, however N-methyl-2-pyrrolidone (NMP) is commonly used.

Hereinafter, the structure of a secondary battery that may bemanufactured by a method for manufacturing a cable-type secondarybattery according to the present invention is described with referenceto FIG. 3, wherein like elements are referred to like referencenumerals.

Referring to FIG. 3, a cable-type secondary battery according to anembodiment of the present invention comprises an inner electrode, anelectrolyte layer 130, an outer electrode, and a protection coating 140.The inner electrode comprises an anode extending longitudinally in aparallel arrangement, and the anode includes a current collector 110 ahorizontal cross section of a predetermined shape and an anode activematerial 111 coated on the current collector 110. The electrolyte layer130 surrounds the inner electrode and serves as an ion channel. Theouter electrode surrounds the electrolyte layer 130, and comprises acathode including a tubular current collector 120 having a horizontalcross section of a predetermined shape and a cathode active material 121coated on the inside of the current collector 120. The protectioncoating 140 surrounds the outer electrode. The anode 110 and 111 or thecathode 120 and 121 of the cable-type secondary battery is formed bycoating an active material on a current collector, preferably byextrusion-coating an electrode slurry including an active material on acurrent collector through an extruder. After the inner electrode, thatis, the anode 110 and 111 is formed, the electrolyte layer 130 may beformed around the inner electrode. Alternatively, after the electrolytelayer 130 is formed, the inner electrode may be inserted into theelectrolyte layer 130. After the inner electrode and the electrolytelayer 130 are formed, the outer electrode and the protection coating 140may be formed on the inner electrode and the electrolyte layer 130.Alternatively, after the electrolyte layer 130, the outer electrode, andthe protection coating 140 are formed, the inner electrode may beinserted into the electrolyte layer 130, or after the outer electrodeand the protection coating 140 are formed, the inner electrode may beinserted and the electrolyte layer 130 may be then formed.

In addition to the cable-type secondary battery of FIG. 3, modifiedcable-type secondary batteries of FIGS. 4 to 6 may be manufactured.

Referring to FIG. 4, a cable-type secondary battery according to anotherembodiment of the present invention comprises an inner electrode, anelectrolyte layer 130, an outer electrode, and a protection coating 140.The inner electrode comprises at least two anodes extendinglongitudinally in a parallel arrangement, each including a currentcollector 110 having a horizontal cross section of a predetermined shapeand an anode active material 111 coated on the current collector 110.The electrolyte layer 130 surrounds the perimeter of the inner electrodeand serves as an ion channel. The outer electrode surrounds theelectrolyte layer 130, and comprises a cathode including a tubularcurrent collector 120 having a horizontal cross section of apredetermined shape and a cathode active material 121 coated on theinside of the current collector 120. The protection coating 140surrounds the outer electrode. As the cable-type secondary battery ofthis embodiment includes a plurality of inner electrodes and a tubularouter electrode, the cable-type secondary battery has an increasedcontact area between the electrodes and the electrolyte and consequentlya high rate. The capacity balance between the inner electrode and theouter electrode may be easily achieved by adjusting the number of theinner electrodes. The anode 110 and 111 or the cathode 120 and 121 ofthe cable-type secondary battery is formed by coating an active materialon a current collector, preferably by extrusion-coating an electrodeslurry including an active material on a current collector through anextruder. After the inner electrode, that is, the anode 110 and 111, isformed, the electrolyte layer 130 may be formed around the perimeter ofthe inner electrode. Alternatively, after the electrolyte layer 130 isformed, the inner electrode may be inserted into the electrolyte layer130. After the inner electrode and the electrolyte layer 130 are formed,the outer electrode and the protection coating 140 may be formed on theinner electrode and the electrolyte layer 130. Alternatively, after theelectrolyte layer 130, the outer electrode, and the protection coating140 are formed, the inner electrode may be inserted into the electrolytelayer 130, or after the outer electrode and the protection coating 140are formed, the inner electrode may be inserted and the electrolytelayer 130 may be then formed.

Referring to FIG. 5, a cable-type secondary battery according to stillanother embodiment of the present invention comprises an innerelectrode, an outer electrode, and a protection coating 140. The innerelectrode comprises at least two anodes extending longitudinally in aparallel arrangement, each including a current collector 110 having ahorizontal cross section of a predetermined shape and an anode activematerial 111 coated on the current collector 110, and an electrolytelayer 130 is formed on the inner electrode and serves as an ion channel.The outer electrode comprises a cathode including a tubular currentcollector 120 and a cathode active material 121 surrounding theperimeter of the inner electrode. The protection coating 140 surroundsthe outer electrode. As the cable-type secondary battery of thisembodiment includes a plurality of inner electrodes and a tubular outerelectrode, the cable-type secondary battery has an increased contactarea between the electrodes and the electrolyte and consequently a highrate. The capacity balance between the inner electrode and the outerelectrode may be easily achieved by adjusting the number of the innerelectrodes. Also, a short circuit may be prevented because theelectrolyte layer 130 is formed on the inner electrode. The anode 110and 111 or the cathode 120 and 121 of the cable-type secondary batteryis formed as an inner electrode by extrusion-coating an electrode slurryincluding an active material on a current collector through an extruder.The electrolyte layer 130 may be then formed on the inner electrode bycoating. The active material 121 of the outer electrode may be coatedaround the perimeter of the inner electrode having the electrolyte layer130. Alternatively, the inner electrode may be inserted into the activematerial 121. After the inner electrode and the active material 121 ofthe outer electrode are formed, the current collector 120 of the outerelectrode and the protection coating 140 may be formed around the innerelectrode and the active material 121. Alternatively, after the activematerial 121 and the current collector 120 of the outer electrode andthe protection coating 140 are formed, the inner electrode may beinserted into the active material 121, or after the current collector120 of the outer electrode and the protection coating 140 are formed,the inner electrode may be inserted and the active material 121 may bethen formed.

Referring to FIG. 6, a cable-type secondary battery according to stillyet another embodiment of the present invention comprises at least oneanode, at least one cathode, a second electrolyte layer 132, and aprotection coating 140. The anode includes a current collector 110having a horizontal cross section of a predetermined shape and an anodeactive material 111 coated on the current collector 110, and a firstelectrolyte layer 131 is formed around the anode and serves as an ionchannel. The cathode comprises a current collector 120 having ahorizontal cross section of a predetermined shape and a cathode activematerial layer 121 coated on the current collector 120. The anode andthe cathode extend longitudinally and are arranged in parallel. Thesecond electrolyte layer 132 commonly surrounds the anode and thecathode, and serves as an ion channel. The protection coating 140surrounds the second electrolyte layer 132. An electrolyte layer may befurther formed around the cathode 120 and 121 to prevent a shortcircuit. As the cable-type secondary battery of this embodiment includesa plurality of anodes and a plurality of cathodes, the cable-typesecondary battery has an increased contact area between the electrodesand the electrolyte and consequently a high rate. The capacity balancebetween the anode and the cathode may be easily achieved by adjustingthe number of the anodes or the number of the cathodes. The anode 110and 111 or the cathode 120 and 121 of the cable-type secondary batteryis formed by extrusion-coating an electrode slurry including an activematerial on a current collector through an extruder. The firstelectrolyte layer 131 may be formed on the anode or the cathode bycoating and the second electrolyte layer 132 may be then simultaneouslyformed around the anode and the cathode. Alternatively, after the secondelectrolyte layer 132 is formed, the anode and the cathode having thefirst electrolyte layer 131 may be inserted into the second electrolytelayer 132. Then, the protection coating 140 may be formed around thesecond electrolyte layer 132. Alternatively, after the secondelectrolyte layer 132 and the protection coating 140 are formed, theanode and the cathode may be inserted into the second electrolyte layer132.

In a method for manufacturing the cable-type secondary battery asdescribed above, it is preferred to form an electrolyte layer byextrusion coating. That is, the method for manufacturing the cable-typesecondary battery of the present invention may further comprise puttinga solid electrolyte material into the extruder, and coating the solidelectrolyte material discharged from the extruder on the surface of theelectrode to form an electrolyte layer which serves as an ion channel.The solid electrolyte material may include a solid electrolyte materialthat can be molten at a high temperature, and a solid electrolytematerial in liquid state that is dissolved in a solvent.

When the electrolyte layer is formed on the anode or the cathode, theuse of continuous coating, in particular, extrusion coating is preferreddue to shape characteristics of the cable-type secondary battery thatextends longitudinally. The solid electrolyte material is put into thehopper 1 of the extruder, is transmitted to the die 5 by the rotation ofthe screw 3 in the cylinder 2, and is coated on the surface of theelectrode through the die 5 mounted at a front part of the cylinder 2,while the electrode is provided to the extruder. The present inventionis not limited to a specific type of die for extrusion coating, howeveran O-die (See FIG. 2) is preferred due to shape characteristics of theelectrode that extends longitudinally. In this instance, the thicknessof a coating layer may be easily controlled by adjusting an extrusionrate of the solid electrolyte material or a linear velocity of theelectrode that represents a supply rate of the electrode to theextruder. When a polymer electrolyte material requiring high temperaturemelting is used as the solid electrolyte material, it is preferred toheat the cylinder 2 of the extruder above the melting point and tomaintain the temperature of the cylinder 2. However, when a solidelectrolyte material in liquid state is used as the solid electrolytematerial, drying may be further performed to remove the solvent.

The solid electrolyte material serving as an ion channel may include agel polymer electrolyte of PEO, PVdF, PMMA, PAN, or PVAc; and a solidpolymer electrolyte of PEO, polyphenylene oxide (PPO), polyetherimide(PEI), polyethersulfone (PES), or PVAc. Even though an polymerelectrolyte has sufficient ion conductivity, ions may move slowly, thatis, a reaction rate may be low, and so the gel polymer electrolytehaving favorable ion movement is preferred over the solid electrolytematerial. Because the gel polymer electrolyte has poor mechanicalproperties, a porous support or a crosslinked polymer may be used toimprove the mechanical properties of the gel polymer electrolyte. Theelectrolyte layer of the present invention may act as a separator,thereby eliminating the use of a separator.

The electrolyte layer of the present invention may further contain alithium salt. The lithium salt may be mixed with electrolyte when theelectrolyte is provided to the extruder. The lithium salt may improveion conductivity and a reaction rate, and may include, but is notlimited to, for example, LiCl, LiBr, LiI, LiClO₄, LiBF₄, LiB₁₀Cl₁₀,LiPF₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆, LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li,(CF₃SO₂)₂NLi, chlorine borane lithium, aliphatic lower lithiumcarbonate, and 4-phenyl lithium borate, singularly or in combination.

The electrolyte layer 130 of FIGS. 3 to 5 and the first and secondelectrolyte layers 131 and 132 of FIG. 6 may be formed around a singleelectrode or a plurality of electrodes by coating the solid electrolytematerial through the extruder. In this instance, when the electrolytelayer surrounds a plurality of electrodes, a modified type of die havinga plurality of openings may be used to fix the electrodes respectively.

Also, the cable-type secondary battery of the present invention has theprotection coating on the outmost surface thereof, and accordingly, themethod for manufacturing a cable-type secondary battery of the presentinvention may further comprise coating the cable-type secondary batterywith a polymer resin discharged from the extruder to form a protectioncoating on the outmost surface of the cable-type secondary battery. Theprotection coating of the present invention that is formed on theoutmost surface of the secondary battery may act as an insulator toprotect the electrode from moisture in the air or from external impact.The protection coating may include typical polymer resins, for example,PVC, high-density polyethylene (HDPE), or epoxy resin.

When the protection coating is formed on the outmost surface of thecable-type secondary battery, the use of continuous coating, inparticular, extrusion coating is preferred due to shape characteristicsof the cable-type secondary battery that extends longitudinally. First,a polymer resin is put into the hopper 1 of the extruder and turns to apolymer resin melt or a polymer resin solution while the polymer resingoes through the cylinder 2 where a constant temperature is maintained,and the polymer resin melt or polymer resin solution is transmitted tothe die 5 by the rotation of the screw 3 in the cylinder 2, and iscoated on the outmost surface of the secondary battery through the die 5mounted at a front part of the cylinder 2. When the polymer resin meltis used, the manufacturing method of the present invention may furthercomprise cooling. When the polymer resin solution is used, themanufacturing method of the present invention may further comprisedrying. In this instance, the thickness of a coating layer may be easilycontrolled by adjusting an extrusion rate of the polymer resin or alinear velocity of the secondary battery. The protection coating ofFIGS. 3 to 6 may be formed by putting a polymer resin into the extruderand by coating the polymer resin on the outmost surface of the secondarybattery.

Hereinafter, the present invention is described in detail throughexamples. However, it should be understood that the detailed descriptionand specific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

EXAMPLE Example 1: Manufacture of a Cable-Type Secondary Battery Havinga Plurality of Anodes

Referring to FIG. 5, the cable-type secondary battery of example 1comprises an anode extending longitudinally and including a currentcollector 110 of a circular cross section and an active material 111coated on the current collector 110; an electrolyte layer 130 formed onthe surface of the anode and serving an ion channel; a cathodesurrounding the perimeter of four anodes having electrolyte layers 130and including a tubular current collector 120 and an active material 121coated on the inside of the tubular current collector 120; and aprotection coating 140 surrounding the cathode.

To manufacture the cable-type secondary battery, first an anode activematerial slurry having a weight ratio of artificial graphite, PVdF,carbon black and NMP=60:16:4:20 was put into a hopper of an extruder.The temperature of a cylinder of the extruder was maintained at 70° C.,and a rotation rate of a screw was maintained between 70 and 80 rpm. Acurrent collector made of a polytetrafluoroethylene (PTFE) wiresurface-treated with copper was provided to an O-die of the extruder ata rate of 3 m/min, and the anode active material slurry wasextrusion-coated on the current collector. The result was dried. In thisway, an anode was formed.

Next, as a solid electrolyte, PEO containing 25 weight % of LiTFSI wasput into the hopper of the extruder. The temperature of the cylinder ofthe extruder was maintained at 50° C., and a rotation rate of the screwwas maintained between 60 and 70 rpm. The solid electrolyte wasextrusion-coated on the surface of the anode while the anode wasprovided to the o-die of the extruder at a rate of 3 m/min. Accordingly,the anode coated with electrolyte was produced.

Then, a cathode was formed by filling a cathode active materialincluding LiCoO₂, PVdF, Denka black, and NMP into a tubular currentcollector of aluminum. The four anodes coated with electrolyte and thecathode were assembled into an electrode assembly.

Finally, PVC was put into the extruder. The temperature of the cylinderof the extruder was maintained at 250° C., and a rotation rate of thescrew was maintained at 100 rpm. A protection coating was formed on theelectrode assembly while the electrode assembly was provided to theO-die at a rate of 30 m/min. As described above, a cable-type secondarybattery was completed.

1. A method for manufacturing a cable-type secondary battery comprisingan electrode extending longitudinally in a parallel arrangement andincluding a current collector having a horizontal cross section of apredetermined shape and an active material layer formed on the currentcollector, the method comprising: forming the electrode, including:putting an electrode slurry including an active material, a polymerbinder, and a solvent into an extruder; extrusion-coating the electrodeslurry on the current collector while continuously providing the currentcollector to the extruder; and drying the current collector coated withthe electrode slurry to form an active material layer.
 2. The method formanufacturing a cable-type secondary battery according to claim 1,wherein the current collector is made from stainless steel, aluminum,nickel, titanium, sintered carbon, and copper; stainless steelsurface-treated with carbon, nickel, titanium, and silver;aluminum-cadmium alloys; non-conductive polymer surface-treated with aconductive material; or conductive polymers.
 3. The method formanufacturing a cable-type secondary battery according to claim 2,wherein the conductive material is any one selected from the groupconsisting of polyacetylene, polyaniline, polypyrrole, polythiophene,polysulfur nitride, indium thin oxide (ITO), silver, palladium, nickel,copper, and mixtures thereof.
 4. The method for manufacturing acable-type secondary battery according to claim 2, wherein theconductive polymer is any one selected from the group consisting ofpolyacetylene, polyaniline, polypyrrole, polythiophene, polysulfurnitride, and mixtures thereof.
 5. The method for manufacturing acable-type secondary battery according to claim 1, wherein the activematerial is an anode active material, and is an active material particleof any one selected from the group consisting of carbonaceous materials;lithium-containing titanium composite oxides (LTOs); metals (Me)including Si, Sn, Li, Zn, Mg, Cd, Ce, Ni, and Fe; alloys of the metals(Me); oxides (MeOx) of the metals (Me); and composites of the metals(Me), carbon, and mixtures thereof.
 6. The method for manufacturing acable-type secondary battery according to claim 1, wherein the activematerial is a cathode active material, and is an active materialparticle of any one selected from the group consisting of LiCoO₂,LiNiO₂, LiMn₂O₄, LiCoPO₄, LiFePO₄, LiNiMnCoO₂, andLiNi_(1-x-y-z)Co_(x)M1 _(y)M2 _(z)O₂ (each of M1 and M2 is independentlyany one selected from the group consisting of Al, Ni, Co, Fe, Mn, V, Cr,Ti, W, Ta, Mg, and Mo, and each of x, y, and z is independently anatomic fraction of each component in the oxide, where 0≦x<0.5, 0≦y<0.5,0≦z<0.5, x+y+z≦1), and mixtures.
 7. The method for manufacturing acable-type secondary battery according to claim 1, wherein the polymerbinder is any one binder polymer selected from the group consisting ofpolyvinylidene fluoride (PVdF)-co-hexafluoropropylene, polyvinylidenefluoride-co-trichloroethylene, polymethylmethacrylate (PMMA),polybutylacrylate, polyacrylonitrile (PAN), polyvinylpyrrolidone,polyvinylacetate (PVAc), polyethylene-co-vinyl acetate, polyethyleneoxide (PEO), polyarylate, cellulose acetate, cellulose acetate butyrate,cellulose acetate propionate, cyanoethylpullulan,cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose,pullulan, carboxyl methyl cellulose, and mixtures thereof.
 8. The methodfor manufacturing a cable-type secondary battery according to claim 1,further comprising: putting a solid electrolyte material into theextruder; and extrusion-coating the solid electrolyte material on theelectrode while continuously providing the electrode to the extruder, toform an electrolyte layer around the electrode.
 9. The method formanufacturing a cable-type secondary battery according to claim 8,wherein the solid electrolyte material includes an electrolyte selectedfrom the group consisting of a gel polymer electrolyte of PEO, PVdF,PMMA, PAN, or PVAc; and a solid polymer electrolyte of PEO,polyphenylene oxide (PPO), polyetherimide (PEI), polyethersulfone (PES),and PVAc.
 10. The method for manufacturing a cable-type secondarybattery according to claim 8, wherein the solid electrolyte materialfurther includes a lithium salt.
 11. The method for manufacturing acable-type secondary battery according to claim 10, wherein the lithiumsalt is any one selected from the group consisting of LiCl, LiBr, LiI,LiClO₄, LiBF₄, LiB₁₀Cl₁₀, LiPE₆, LiCF₃SO₃, LiCF₃CO₂, LiAsF₆, LiSbF₆,LiAlCl₄, CH₃SO₃Li, CF₃SO₃Li, (CF₃SO₂)₂NLi, chlorine borane lithium,aliphatic lower lithium carbonate, 4-phenyl lithium borate, and mixturesthereof.
 12. A method for manufacturing a cable-type secondary battery,the method comprising: forming an anode by extrusion-coating anelectrode slurry on a current collector, the anode having a horizontalcross section of a predetermined shape and extending longitudinally;forming an electrolyte layer around the perimeter of an inner electrodeby extrusion-coating a solid electrolyte material, the inner electrodeincluding at least two anodes arranged in parallel; forming an outerelectrode around the electrolyte layer, the outer electrode being atubular cathode having a horizontal cross section of a predeterminedshape; and forming a protection coating around the outer electrode. 13.A method for manufacturing a cable-type secondary battery, the methodcomprising: forming an anode having an electrolyte layer thereon bysequentially extrusion-coating an electrode slurry and a solidelectrolyte material on a current collector, the anode having ahorizontal cross section of a predetermined shape and extendinglongitudinally; forming an outer electrode having a cathode activematerial layer, the cathode active material layer surrounding theperimeter of the inner electrode including at least two anodes arrangedin parallel; and forming a protection coating around the outerelectrode.
 14. A method for manufacturing a cable-type secondarybattery, the method comprising: forming an anode having a firstelectrolyte layer thereon by sequentially extrusion-coating an electrodeslurry and a solid electrolyte material on a current collector, theanode having a horizontal cross section of a predetermined shape andextending longitudinally; forming a cathode by extrusion-coating anelectrode slurry on a current collector; forming a second electrolytelayer around the perimeter of an inner electrode by extrusion-coating asolid electrolyte material, the inner electrode including the anode andthe cathode arranged in parallel; and forming a protection coatingaround the second electrolyte layer.